Electrosurgical hemostatic devices have been used for effecting improved hemostasis by heating tissue and blood vessels to cause coagulation or cauterization. Monopolar devices utilize one electrode associated with the cutting or cauterizing instruments and a remote return, usually adhered externally to the patient. More recently bipolar instruments have been used because the coagulating current is generally limited to the tissue between two poles or electrodes of the tissue treating portion of an instrument.
Bipolar forceps have also been used, particularly for coagulating tissue in various procedures. Generally bipolar forceps are comprised of two opposing jaws each of a different electrical potential. The jaws are used to grasp tissue between the two poles and apply electrical current through the grasped tissue. The forceps however tend to cause areas of thermal spread, i.e., dissipation of heat outside the area defined by the grasping or engaging surfaces of the forceps. Other drawbacks of known bipolar forceps include the tendency of current to arc between the electrodes or poles when tissue is too thin, or, the tendency of the forceps to short when the electrodes or poles of the forceps touch.
U.S. application Ser. No. 08/095,797 filed on Jun. 22, 1993, now U.S. Pat. No. 5,403,312, illustrates, in a preferred embodiment, a clamping and coagulating device in which most of the tissue being treated by the end effector of the device is not visible to the user. The electrodes in the preferred embodiment of this device are offset from each other with respect to the tissue grasping surfaces so that the likelihood of arcing or shorting is reduced. However, in this device it is difficult to visualize coagulation as it is occurring to the tissue unless thermal spread is occurring.
It is therefore an object of the present invention to provide an electrosurgical device in which the coagulation can be perceptibly monitored by a user of the device.